An electronic control unit for an internal combustion engine comprises a PCB (Printed Circuit Board), which supports an electronic circuit, a plurality of electric/electronic components electrically connected to the electric circuit, and at least one connector electrically connected to the electric circuit for connecting the electronic control unit to the internal combustion engine wiring. The printed circuit board is accommodated in a housing, which comprises a base which inferiorly supports the printed circuit board and a lid which superiorly closes the base.
An electronic control unit for an internal combustion engine is normally arranged inside an engine compartment near the internal combustion engine to be controlled; consequently, the electronic control unit must be capable of withstanding thermal stresses (from the low temperatures that a car parked in the open during the winter may reach to the high temperatures reached inside the engine compartment during operation of the internal combustion engine in summer), and mechanical stresses (vibrations deriving directly from the internal combustion engine, inertia stress deriving from driving the vehicle, and pulse stresses deriving from the road surface roughness/irregularities) alike without damage.
It has been observed that large-sized electric/electronic components (i.e. electrolytic capacitors) are particularly prone to mechanical stresses, because they are only inferiorly fixed (welded) to the printed circuit board and present a heavy mass (and thus a high mechanical inertia) having a center of gravity relatively distant from the printed circuit board.
In order to attempt to increase the mechanical strength of a large-sized electric/electrolytic component, it has been suggested to perform a peripheral resin-coating of the electric/electronic component itself at the printed board circuit; alternatively, it has been suggested to fix a plastic frame which surrounds and withholds the large-sized electric/electronic component to the printed circuit board. The mechanical solutions described above, however, while being effective are costly because they require additional, highly automated machining operations.
Patents DE2823666A1 and U.S. Pat. No. 6,123,565 A1 describe an electronic control unit for automotive applications, wherein the housing is completely filled with an expanded foam to limit the vibrations which are transmitted to the electric/electronic components; however, this constructive solution implies various drawbacks because it is costly, difficult to implement and makes any repair intervention on the electronic control unit extremely complicated.